Communication System, Station-Side Optical Line Terminating Apparatus, User-Side Optical Line Terminating Apparatus, Control Apparatus, and Communication Method

1. A communication system in which a plurality of user-side optical line terminating apparatuses (Optical Network Units, hereinafter referred to as ONUs) and station-side optical line terminating apparatus (Optical Line Terminal, hereinafter referred to as OLT) are connected with a common optical fiber, wherein the ONUs each include: an ONU side optical transceiver having a transmitting function that is configured to be turned off in a period of sleep time to reduce power consumption in a power saving mode; and an ONU control device configured to receive the period of sleep time from the OLT and store the period of sleep time, and turn off, upon receiving an instruction for shifting to the power saving mode from the OLT, the transmitting function of the ONU side optical transceiver in the period of sleep time designated by the OLT via the ONU side optical transceiver, wherein the OLT includes: an OLT side optical transceiver connected to the optical fiber; and an OLT control device configured to send separate messages to each of at least two ONUs to separately designate the period of sleep time for each of the at least two ONUs via the OLT side optical transceiver.

2. The communication system according to claim 1 , wherein the OLT control device is configured to transmit an instruction for shifting to the power saving mode to the ONU via the OLT side optical transceiver.

3. The communication system according to claim 1 , wherein the ONU control device is configured to turn-off the transmitting function of the ONU side optical transceiver in the period of sleep time, the period of sleep time being a maximum sleep time allowed by the OLT.

4. The communication system according to claim 1 , wherein the transmitting function is configured to be powered-off and powered-on repeatedly in the power saving mode.

5. A station-side optical line terminating apparatus connected to a plurality of user-side optical line terminating apparatuses with a common optical fiber, the station-side optical line terminating apparatus comprising: an optical transceiver connected to the optical fiber; and a control device configured to send separate messages to each of at least two user-side optical line terminating apparatuses to separately designate a period of sleep time for each of the at least two user-side optical line terminating apparatuses via the optical transceiver, wherein the period of sleep time sent from the control device is received and stored at each of the at least two user-side optical line terminating apparatuses, and a transmitting function in each of the at least two user-side optical line terminating apparatuses are turned off in the period of sleep time in a power saving mode to reduce power consumption upon receiving an instruction for shifting to a power saving mode from the station-side optical line terminating apparatus.

6. The station-side optical line terminating apparatus according to claim 5 , wherein the control device is configured to transmit an instruction for shifting to the power saving mode to the user-side optical line terminating apparatus.

7. The station-side optical line terminating apparatus according to claim 5 , wherein the transmitting function is configured to be powered-off and powered-on repeatedly in the power saving mode.

8. A user-side optical line terminating apparatus for a communication system in which a plurality of the user-side optical line terminating apparatuses are connected to a station-side optical line terminating apparatus with an optical fiber, the user-side optical line terminating apparatus comprising: an optical transceiver, connected to the optical fiber, and having a transmitting function that is configured to be turned off to reduce power consumption in a power saving mode; and a control device configured to receive a message separately sent to each of at least two user-side optical line terminating apparatuses, via the optical transceiver, to separately designate a period of sleep time for each of the at least two user-side optical line terminating apparatuses, store the period of sleep time, and turn off, upon receiving an instruction for shifting to the power saving mode from the station-side optical line terminating apparatus, the transmitting function of the optical transceiver in the period of sleep time.

9. The user-side optical line terminating apparatus according to claim 8 , wherein the transmitting function is configured to be powered-off and powered-on repeatedly in the power saving mode.

10. The user-side optical line terminating apparatus according to claim 8 , wherein the control device is configured to turn off the transmitting function of the optical transceiver in the period of sleep time, the period of sleep time being a maximum sleep time allowed by the station-side optical terminating apparatus.

11. A communication method for a communication system in which a plurality of slave station apparatuses are connected to a master station apparatus by a communication line, the communication method comprising: transmitting, by the master station apparatus, separate messages to each of at least two slave station apparatuses to separately designate a period of sleep time for turning off a transmitting function in each of the at least two of the slave station apparatuses; receiving the period of sleep time from the master station apparatus at each of the at least two slave station apparatuses; storing the period of sleep time at each of the at least two slave station apparatuses; and turning off the transmitting function in each of the at least two slave station apparatuses in the period of sleep time, upon receiving an instruction for shifting to a power saving mode from the master station.

12. The communication method for a communication system according to claim 11 , wherein the transmitting function is configured to be powered-off and powered-on repeatedly in the power saving mode.

13. A control apparatus of a master station apparatus connected to a plurality of slave station apparatuses using an optical fiber and configured to communicate with the slave station apparatuses via an optical transceiver, wherein: in a power saving mode in which a transmitting function of the slave station apparatus is turned off in a period of sleep time, the control apparatus is configured to send separate messages to each of at least two slave station apparatuses to separately designate the period of sleep time for each of the at least two slave station apparatuses, via the optical transceiver and the period of sleep time sent from the control device is received and stored at each of the at least two slave station apparatuses, and the transmitting function in each of the at least two slave station apparatuses is turned off in the period of sleep time in the power saving mode to reduce power consumption.

14. The control apparatus of a master station apparatus according to claim 13 , wherein the transmitting function is configured to be powered-off and powered-on repeatedly in the power saving mode.

15. A control apparatus of a slave station apparatus for a communication system in which a plurality of slave station apparatuses are connected to a master station apparatus using an optical fiber and configured to communicate with the master station apparatus using an optical transceiver, wherein: the control apparatus receives a message separately sent by the master station apparatus to each of at least two slave station apparatuses, via the optical transceiver, to separately designate a period of sleep time for each of the at least two slave station apparatuses, stores the period of sleep time, and turns off a transmitting function of the optical transceiver in the period of sleep time, upon receiving an instruction for shifting to the power saving mode.

16. The control apparatus of a slave station apparatus according to claim 15 , wherein the transmitting function is configured to be powered-off and powered-on repeatedly in the power saving mode.